Comparison of the characteristics of plant and animal cells. Cell structure, difference between a plant cell and an animal cell

The cells of animals and plants, both multicellular and unicellular, are in principle similar in structure. Differences in the details of cell structure are associated with their functional specialization.

The main elements of all cells are the nucleus and cytoplasm. The nucleus has a complex structure, changing to different phases cell division, or cycle. The nucleus of a nondividing cell occupies approximately 10–20% of its total volume. It consists of karyoplasm (nucleoplasm), one or more nucleoli (nucleoli) and a nuclear membrane. Karyoplasm is a nuclear sap, or karyolymph, in which there are strands of chromatin that form chromosomes.

Basic properties of the cell:

• metabolism
• sensitivity
• reproductive capacity

The cell lives in internal environment body - blood, lymph and tissue fluid. The main processes in the cell are oxidation and glycolysis - the breakdown of carbohydrates without oxygen. Cell permeability is selective. It is determined by the reaction to high or low salt concentrations, phago- and pinocytosis. Secretion is the formation and release by cells of mucus-like substances (mucin and mucoids), which protect against damage and participate in the formation of intercellular substance.

Types of cell movements:

1. amoeboid (pseudopods) – leukocytes and macrophages.
2. sliding – fibroblasts
3. flagellar type – spermatozoa (cilia and flagella)

Cell division:

1. indirect (mitosis, karyokinesis, meiosis)
2. direct (amitosis)

During mitosis, the nuclear substance is distributed evenly between daughter cells, because Nuclear chromatin is concentrated in chromosomes, which split into two chromatids that separate into daughter cells.

Structures of a living cell

Chromosomes

Mandatory elements of the nucleus are chromosomes, which have a specific chemical and morphological structure. They take an active part in the metabolism in the cell and are directly related to the hereditary transmission of properties from one generation to another. It should, however, be borne in mind that although heredity is ensured by the entire cell as a single system, nuclear structures, namely chromosomes, occupy a special place in this. Chromosomes, unlike cell organelles, are unique structures characterized by constant qualitative and quantitative composition. They cannot replace each other. Imbalance chromosome set cells ultimately leads to its death.

Cytoplasm

The cytoplasm of the cell exhibits a very complex structure. The introduction of thin sectioning techniques and electron microscopy made it possible to see the fine structure of the underlying cytoplasm. It has been established that the latter consists of parallel complex structures in the form of plates and tubules, on the surface of which there are tiny granules with a diameter of 100–120 Å. These formations are called the endoplasmic complex. This complex includes various differentiated organelles: mitochondria, ribosomes, Golgi apparatus, in the cells of lower animals and plants - centrosome, in animals - lysosomes, in plants - plastids. In addition, the cytoplasm reveals a number of inclusions that take part in the cell’s metabolism: starch, fat droplets, urea crystals, etc.

Membrane

The cell is surrounded by a plasma membrane (from the Latin “membrane” - skin, film). Its functions are very diverse, but the main one is protective: it protects the internal contents of the cell from influences external environment. Thanks to various outgrowths and folds on the surface of the membrane, the cells are firmly connected to each other. The membrane is permeated with special proteins through which certain substances needed by the cell or to be removed from it can move. Thus, metabolism occurs through the membrane. Moreover, what is very important, substances are passed through the membrane selectively, due to which the required set of substances is maintained in the cell.

In plants, the plasma membrane is covered on the outside with a dense membrane consisting of cellulose (fiber). The shell performs protective and supporting functions. It serves as the outer frame of the cell, giving it a certain shape and size, preventing excessive swelling.

Core

Located in the center of the cell and separated by a two-layer membrane. It has a spherical or elongated shape. The shell - karyolemma - has pores necessary for the exchange of substances between the nucleus and the cytoplasm. The contents of the nucleus are liquid - karyoplasm, which contains dense bodies - nucleoli. They secrete granules - ribosomes. The bulk of the nucleus is nuclear proteins - nucleoproteins, in the nucleoli - ribonucleoproteins, and in the karyoplasm - deoxyribonucleoproteins. The cell is covered with a cell membrane, which consists of protein and lipid molecules that have a mosaic structure. The membrane ensures the exchange of substances between the cell and the intercellular fluid.

EPS

This is a system of tubules and cavities, on the walls of which there are ribosomes that provide protein synthesis. Ribosomes can be freely located in the cytoplasm. There are two types of EPS - rough and smooth: on the rough EPS (or granular) there are many ribosomes that carry out protein synthesis. Ribosomes give membranes their rough appearance. Smooth ER membranes do not carry ribosomes on their surface; they contain enzymes for the synthesis and breakdown of carbohydrates and lipids. Smooth EPS looks like a system of thin tubes and tanks.

Ribosomes

Small bodies with a diameter of 15–20 mm. They synthesize protein molecules and assemble them from amino acids.

Mitochondria

These are double-membrane organelles, the inner membrane of which has projections - cristae. The contents of the cavities are matrix. Mitochondria contain a large number of lipoproteins and enzymes. These are the energy stations of the cell.

Plastids (characteristic only of plant cells!)

Their contents in the cell are main feature plant organism. There are three main types of plastids: leucoplasts, chromoplasts and chloroplasts. They have different colors. Colorless leucoplasts are found in the cytoplasm of cells of uncolored parts of plants: stems, roots, tubers. For example, there are many of them in potato tubers, in which starch grains accumulate. Chromoplasts are found in the cytoplasm of flowers, fruits, stems, and leaves. Chromoplasts provide yellow, red, and orange colors to plants. Green chloroplasts are found in the cells of leaves, stems and other parts of the plant, as well as in a variety of algae. Chloroplasts are 4-6 microns in size and often have an oval shape. In higher plants, one cell contains several dozen chloroplasts.

Green chloroplasts are able to transform into chromoplasts - that’s why the leaves turn yellow in the fall, and green tomatoes turn red when ripe. Leukoplasts can transform into chloroplasts (greening of potato tubers in the light). Thus, chloroplasts, chromoplasts and leucoplasts are capable of mutual transition.

The main function of chloroplasts is photosynthesis, i.e. In chloroplasts, in the light, organic substances are synthesized from inorganic ones due to the conversion of solar energy into the energy of ATP molecules. The chloroplasts of higher plants are 5-10 microns in size and resemble in shape biconvex lens. Each chloroplast is surrounded by a double membrane that is selectively permeable. The outside is a smooth membrane, and the inside has a folded structure. The main structural unit of the chloroplast is the thylakoid, a flat double-membrane sac that plays a leading role in the process of photosynthesis. The thylakoid membrane contains proteins similar to mitochondrial proteins that participate in the electron transport chain. The thylakoids are arranged in stacks resembling stacks of coins (10 to 150) called grana. Grana has a complex structure: chlorophyll is located in the center, surrounded by a layer of protein; then there is a layer of lipoids, again protein and chlorophyll.

Golgi complex

This is a system of cavities delimited from the cytoplasm by a membrane and can have different shapes. The accumulation of proteins, fats and carbohydrates in them. Carrying out the synthesis of fats and carbohydrates on membranes. Forms lysosomes.

The main structural element of the Golgi apparatus is the membrane, which forms packets of flattened cisterns, large and small vesicles. The cisterns of the Golgi apparatus are connected to the channels of the endoplasmic reticulum. Proteins, polysaccharides, and fats produced on the membranes of the endoplasmic reticulum are transferred to the Golgi apparatus, accumulate inside its structures and are “packaged” in the form of a substance, ready either for release or for use in the cell itself during its life. Lysosomes are formed in the Golgi apparatus. In addition, it is involved in the growth of the cytoplasmic membrane, for example during cell division.

Lysosomes

Bodies delimited from the cytoplasm by a single membrane. The enzymes they contain accelerate the breakdown of complex molecules into simple ones: proteins into amino acids, complex carbohydrates to simple, lipids to glycerol and fatty acids, and also destroy dead parts of the cell, whole cells. Lysosomes contain more than 30 types of enzymes (protein substances that increase the speed chemical reaction tens and hundreds of thousands of times), capable of breaking down proteins, nucleic acids, polysaccharides, fats and other substances. The breakdown of substances with the help of enzymes is called lysis, hence the name of the organelle. Lysosomes are formed either from the structures of the Golgi complex or from the endoplasmic reticulum. One of the main functions of lysosomes is participation in intracellular digestion nutrients. In addition, lysosomes can destroy the structures of the cell itself when it dies, during embryonic development, and in a number of other cases.

Vacuoles

They are cavities in the cytoplasm filled with cell sap, a place where reserve nutrients accumulate, harmful substances; they regulate the water content in the cell.

Cell center

It consists of two small bodies - centrioles and centrosphere - a compacted section of the cytoplasm. Playing important role during cell division

Cell movement organelles

1. Flagella and cilia, which are cell outgrowths and have the same structure in animals and plants
2. Myofibrils are thin filaments more than 1 cm long with a diameter of 1 micron, located in bundles along the muscle fiber
3. Pseudopodia (perform the function of movement; due to them, muscle contraction occurs)

Similarities between plant and animal cells

The characteristics that are similar between plant and animal cells include the following:

1. Similar structure of the structure system, i.e. presence of nucleus and cytoplasm.
2. The metabolic process of substances and energy is similar in principle.
3. Both animal and plant cells have a membrane structure.
4. The chemical composition of the cells is very similar.
5. Plant and animal cells undergo a similar process of cell division.
6. Plant cells and animal cells have the same principle of transmitting the code of heredity.

Significant differences between plant and animal cells

In addition to the general signs of the structure and vital activity of plant and animal cell, there are also special distinctive features each of them.

Thus, we can say that plant and animal cells are similar to each other in the content of some important elements and some vital processes, and also have significant differences in structure and metabolic processes.

A cell is a structural and functional unit of a living organism that carries genetic information, provides metabolic processes, and is capable of regeneration and self-reproduction.

There are unicellular individuals and developed multicellular animals and plants. Their vital activity is ensured by the work of organs that are built from different tissues. Tissue, in turn, is represented by a collection of cells similar in structure and functions.

Cells different organisms have their own characteristic properties and structure, but there are common components inherent in all cells: both plant and animal.

Organelles common to all cell types

Core- one of important components cells, contains genetic information and ensures its transmission to descendants. It is surrounded by a double membrane, which isolates it from the cytoplasm.

Cytoplasm- a viscous transparent medium that fills the cell. All organelles are located in the cytoplasm. The cytoplasm consists of a system of microtubules, which ensures the precise movement of all organelles. It also controls the transport of synthesized substances.

Cell membrane– a membrane that separates the cell from the external environment, ensures the transport of substances into the cell and the removal of products of synthesis or vital activity.

Endoplasmic reticulum– a membrane organelle, consists of cisterns and tubules, on the surface of which ribosomes are synthesized (granular EPS). Places where there are no ribosomes form the smooth endoplasmic reticulum. The granular and agranular network are not delimited, but pass into each other and connect to the core shell.

Golgi complex- a stack of tanks, flattened in the center and expanded at the periphery. Designed to complete the synthesis of proteins and their further transport from the cell; together with EPS, it forms lysosomes.

Mitochondria– double-membrane organelles, the inner membrane forms protrusions into the cell – cristae. Responsible for ATP synthesis and energy metabolism. Performs respiratory function(absorbing oxygen and releasing CO 2).

Ribosomes– are responsible for protein synthesis; small and large subunits are distinguished in their structure.

Lysosomes– carry out intracellular digestion due to the content of hydrolytic enzymes. Break down trapped foreign substances.

In both plant and animal cells, in addition to organelles, there are unstable structures - inclusions. They appear when increasing metabolic processes in a cage. They perform a nutritional function and contain:

• Starch grains in plants, and glycogen in animals;
• proteins;
• Lipids are high-energy compounds that are more valuable than carbohydrates and proteins.

There are inclusions that do not play a role in energy metabolism, they contain waste products of the cell. IN glandular cells animal inclusions accumulate secretions.

Organelles unique to plant cells

Animal cells, unlike plant cells, do not contain vacuoles, plastids, or a cell wall.

Cell wall is formed from the cell plate, forming the primary and secondary cell walls.

The primary cell wall is found in undifferentiated cells. During maturation, a secondary membrane is formed between the membrane and the primary cell wall. In its structure it is similar to the primary one, only it has more cellulose and less water.

The secondary cell wall is equipped with many pores. A pore is a place where there is no secondary wall between the primary shell and the membrane. The pores are located in pairs in adjacent cells. Cells located nearby communicate with each other by plasmodesmata - this is a channel that is a strand of cytoplasm lined with plasmolemma. Through it, cells exchange synthesized products.

Functions of the cell wall:

1. Maintaining cell turgor.
2. Gives shape to cells, acting as a skeleton.
3. Accumulates nutritious foods.
4. Protects from external influences.

Vacuoles– organelles filled with cell sap are involved in the digestion of organic substances (similar to the lysosomes of an animal cell). They are formed through the joint work of the ER and the Golgi complex. First, several vacuoles form and function; during cell aging, they merge into one central vacuole.

Plastids- autonomous double-membrane organelles, the inner shell has outgrowths - lamellae. All plastids are divided into three types:

• Leukoplasts– non-pigmented formations, capable of storing starch, proteins, lipids;
• chloroplasts– green plastids, contain the pigment chlorophyll, capable of photosynthesis;
• chromoplasts– crystals orange color, due to the presence of the pigment carotene.

Organelles unique to animal cells

The difference between a plant cell and an animal cell is the absence of a centriole, a three-layer membrane.

Centrioles– paired organelles located near the nucleus. They take part in the formation of the spindle and contribute to the uniform divergence of chromosomes to different poles of the cell.

Plasma membrane— animal cells are characterized by a three-layer, durable membrane, built from lipids and proteins.

Comparative characteristics of plant and animal cells

Plant cells, thanks to chloroplasts, carry out the processes of photosynthesis - convert the energy of the sun into organic matter, animal cells are not capable of this.

Mitotic division of a plant occurs predominantly in the meristem, characterized by the presence of an additional stage - preprophase; in the animal body, mitosis is inherent in all cells.

The sizes of individual plant cells (about 50 microns) exceed the sizes of animal cells (about 20 microns).

The relationship between plant cells is carried out through plasmodesmata, and in animals - through desmosomes.

Vacuoles in a plant cell occupy most of its volume; in animals they are small formations in small quantities.

The cell wall of plants is made of cellulose and pectin; in animals, the membrane consists of phospholipids.

Plants are not able to actively move, so they have adapted to the autotrophic method of nutrition, independently synthesizing all the necessary nutrients from inorganic compounds.

Animals are heterotrophs and use exogenous organic substances.

The similarity in the structure and functionality of plant and animal cells indicates the unity of their origin and belonging to eukaryotes. Their distinctive features are due to in different ways life and nutrition.

The cells of animals and plants, both multicellular and unicellular, are in principle similar in structure. Differences in the details of cell structure are associated with their functional specialization.

The main elements of all cells are the nucleus and cytoplasm. The nucleus has a complex structure that changes at different phases of cell division, or cycle. The nucleus of a non-dividing cell occupies approximately 10-20% of its total volume. It consists of karyoplasm (nucleoplasm), one or more nucleoli (nucleoli) and a nuclear membrane. Karyoplasm is a nuclear sap, or karyolymph, in which there are strands of chromatin that form chromosomes.

Mandatory elements of the nucleus are chromosomes, which have a specific chemical and morphological structure. They take an active part in the metabolism in the cell and are directly related to the hereditary transmission of properties from one generation to another.

The cytoplasm of the cell exhibits a very complex structure. The introduction of thin sectioning techniques and electron microscopy made it possible to see the fine structure of the underlying cytoplasm.

It has been established that the latter consists of parallel complex structures in the form of plates and tubules, on the surface of which there are tiny granules with a diameter of 100-120 Å. These formations are called the endoplasmic complex. This complex includes various differentiated organelles: mitochondria, ribosomes, the Golgi apparatus, in the cells of animals and lower plants - the centrosome, in animals - lysosomes, in plants - plastids. In addition, the cytoplasm reveals a number of inclusions that take part in the cell’s metabolism: starch, fat droplets, urea crystals, etc.

Centrioles(cellular center) consists of two components: triplets and centrosphere - in a special way differentiated area of ​​the cytoplasm. Centrioles consist of two small rounded rings. An electron microscope shows that these bodies are a system of strictly oriented tubes.

Mitochondria there are in cells different shapes: rod-shaped, null-shaped, etc. It is believed that their shape can vary depending on functional state cells. The sizes of mitochondria vary widely: from 0.2 to 2-7 microns. in cells of different tissues they are located either evenly throughout the cytoplasm, or with a higher concentration in certain areas. It has been established that mitochondria take part in the oxidative processes of cell metabolism. Mitochondria are composed of proteins, lipids and nucleic acids. A number of enzymes involved in aerobic oxidation, as well as those associated with phosphorylation, were found in them. It is believed that all reactions of the Krebs cycle occur in mitochondria: most of the energy is released while the energy is spent on the work of the cell.

The structure of mitochondria turned out to be complex. According to electron microscopic studies, they are bodies, narrowed by a hydrophilic sol, enclosed in a selectively permeable shell - a membrane, the thickness of which is about 80 Å. Mitochondria have a layered structure in the form of a system of morning ridges-crystals, the thickness of which is 180-200 Å. They are moving away from inner surface membranes, forming ring-shaped diaphragms. It is assumed that mitochondria reproduce by fission. When cells divide, their distribution among the outermost cells does not follow a strict pattern, since %, apparently, can quickly multiply to the number required by the cell. By shape, size and role in biochemical processes Mitochondria are characteristic of each type of organism.

At biochemical research microsomes are found in the cytoplasm, which are fragments of membranes with the structure of the endoplasmic reticulum.

There are significant amounts of ribosomes in the cytoplasm; their sizes vary from 150 to 350 Å and are invisible in a light microscope. Their special feature is high content RNA and proteins: About 50% of all cellular RNA is found in ribosomes, indicating great importance last in cell activity. It has been established that ribosomes are involved in the synthesis of cellular proteins under the control of the nucleus. The reproduction of the ribosomes themselves is also controlled by the nucleus; in the absence of a nucleus, they lose the ability to synthesize cytoplasmic proteins and disappear.

The cytoplasm also contains Golgi apparatus. It represents a system of smooth membranes and tubules located around the nucleus or polar. It is believed that this device provides excretory function cells. Fine structure it remains unclear.

Organelles of the cytoplasm are also lysosomes- lytic bodies that perform the function of digestion inside the cell. They have been discovered so far only in animal cells. Lysosomes contain active juice - a number of enzymes capable of breaking down proteins, nucleic acids and polysaccharides entering the cell. If the lysosome membrane ruptures and the enzymes move into the cytoplasm, they “digest” other elements, the cytoplasm, and lead to the dissolution of the cell - “self-eating”.

The cytoplasm of plant cells is characterized by the presence of plastids, which carry out photosynthesis, the synthesis of starch and pigments, as well as proteins, lipids and nucleic acids. Based on color and function, plastids can be divided into three groups: leucoplasts, chloroplasts and chromoplasts. Leukoplasts are colorless plastids involved in the synthesis of starch from sugars. Chloroplasts are protein bodies of a denser consistency than the cytoplasm; Along with proteins, they contain a lot of lipids. The protein body (stroma) of chloroplasts carries pigments, mainly chlorophyll, which explains their green color; chloroplasts carry out photosynthesis. Chromoplasts contain pigments - carotenoids (carotene and xanthophyll).

Plastids reproduce by direct division and, apparently, do not arise anew in the cell. Until now, we do not know the principle of their distribution among daughter cells during division. It is possible that there is no strict mechanism to ensure equal distribution, since the required number can be quickly restored. During asexual and sexual reproduction of plants, traits determined by the properties of plastids can be inherited through the maternal cytoplasm.

Here we will not dwell on the features of changes in individual elements of the cell in connection with the functions they perform. physiological functions, since it falls within the field of study of cytology, cytochemistry, cytophysics and cytophysiology. However, it should be noted that in Lately researchers come to a very important conclusion regarding chemical characteristics organelles of the cytoplasm: a number of them, such as mitochondria, plastids and even centrioles, have their own DNA. What the role of DNA is and what state it is in remains unclear.

We became acquainted with the general structure of the cell only in order to subsequently evaluate the role of its individual elements in ensuring material continuity between generations, that is, in heredity, because all the structural elements of the cell take part in its preservation. It should, however, be borne in mind that although heredity is ensured by the entire cell as a single system, nuclear structures, namely chromosomes, occupy a special place in this. Chromosomes, unlike cell organelles, are unique structures characterized by constant qualitative and quantitative composition. They cannot replace each other. An imbalance in the chromosomal complement of a cell ultimately leads to its death.

According to their structure, the cells of all living organisms can be divided into two large sections: non-nuclear and nuclear organisms.

In order to compare the structure of plant and animal cells, it should be said that both of these structures belong to the superkingdom of eukaryotes, which means they contain a membrane membrane, a morphologically shaped nucleus and organelles for various purposes.

Features of the structure of a plant cell:

Features of the structure of an animal cell:

Brief comparison of plant and animal cells

What follows from this

1. The fundamental similarity in the structural features and molecular composition of plant and animal cells indicates the relationship and unity of their origin, most likely from single-celled organisms. aquatic organisms.
2. Both types contain many elements periodic table, which mainly exist in the form of complex compounds of inorganic and organic nature.
3. However, what is different is that in the process of evolution these two types of cells have moved far away from each other, because from various adverse environmental influences they have absolutely different ways protection and also have different feeding methods from each other.
4. A plant cell is mainly distinguished from an animal cell by its strong shell, consisting of cellulose; special organelles - chloroplasts with chlorophyll molecules in their composition, with the help of which we carry out photosynthesis; and well-developed vacuoles with a supply of nutrients.

Animal and plant cells. Comparison.

Before starting the comparison, it is necessary to mention once again (although this has already been said more than once) that both plant and animal cells are united (together with fungi) into the superkingdom of eukaryotes, and for cells of this superkingdom the presence of a membrane membrane, a morphologically separate nucleus and cytoplasm is typical (matrix) containing various organelles and inclusions.

So, a comparison of animal and plant cells: General signs: 1. Unity of structural systems - cytoplasm and nucleus. 2. The similarity of metabolic and energy processes. 3. Unity of the principle of hereditary code. 4. Universal membrane structure. 5. Unity chemical composition. 6. Similarities in the process of cell division.

Eukaryotic cell

Rice. 1. Scheme of the structure of a eukaryotic cell: 1 - nucleus; 2 - nucleolus; 3 - pores of the nuclear membrane; 4 - mitochondria; 5 - endocytic invagination; 6 - lysosome; 7 - agranular endoplasmic reticulum; 8 - granular endoplasmic reticulum with polysomes; 9 - ribosomes; 10 - Golgi complex; 11 - plasma membrane. Arrows indicate the direction of flow during endo- and exocytosis.

Scheme of the structure of the plasma membrane:

Rice. 2. Scheme of the structure of the plasma membrane: 1 - phospholipids; 2 - cholesterol; 3 - integral protein; 4 - oligosaccharide side chain.

Electron diffraction pattern of the cell center (two centrioles at the end of the G1 period of the cell cycle):